17 May 2010: Analysis

The Anthropocene Debate: Marking Humanity’s Impact

Is human activity altering the planet on a scale comparable to major geological events of the past? Scientists are now considering whether to officially designate a new geological epoch to reflect the changes that homo sapiens have wrought: the Anthropocene.

by elizabeth kolbert

The Holocene — or “wholly recent” epoch — is what geologists call the 11,000 years or so since the end of the last ice age. As epochs go, the Holocene is barely out of diapers; its immediate predecessor, the Pleistocene, lasted more than two million years, while many earlier epochs, like the Eocene, went on for more than 20 million years. Still, the Holocene may be done for. People have become such a driving force on the planet that many geologists argue a new epoch — informally dubbed the Anthropocene — has begun.

In a recent paper titled “The New World of the Anthropocene,” which appeared in the journal Environmental Science and Technology, a group of geologists listed more than a half dozen human-driven processes that are likely to leave a lasting mark on the planet — lasting here understood to mean likely to leave traces that will last tens of millions of years. These include: habitat destruction and the introduction of invasive species, which are causing widespread extinctions; ocean acidification, which is changing the chemical makeup of the seas; and urbanization, which is vastly increasing rates of sedimentation and erosion.

Human activity, the group wrote, is altering the planet “on a scale comparable with some of the major events of the ancient past. Some of these changes are now seen as permanent, even on a geological time-scale.”

Prompted by the group’s paper, the Independent of London last month conducted a straw poll of the members of the International Commission on

Are we living in the Anthropocene? The answer, the group of geologists concluded, was probably yes.

Stratigraphy, the official keeper of the geological time scale. Half the commission members surveyed said they thought the case for a new epoch was already strong enough to consider a formal designation.

“Human activities, particularly since the onset of the industrial revolution, are clearly having a major impact on the Earth,” Barry Richards of the Geological Survey of Canada told the newspaper. “We are leaving a clear and unique record.”

The term “Anthropocene” was coined a decade ago by Paul Crutzen, one of the three chemists who shared the 1995 Nobel Prize for discovering the effects of ozone-depleting compounds. In a paper published in 2000, Crutzen and Eugene Stoermer, a professor at the University of Michigan, noted that many forms of human activity now dwarf their natural counterparts; for instance, more nitrogen today is fixed synthetically than is fixed by all the world’s plants, on land and in the ocean. Considering this, the pair wrote in the newsletter of the International Geosphere-Biosphere Programme, “it seems to us more than appropriate to emphasize the central role of mankind in geology and ecology by proposing to use the term ‘anthropocene’ for the current geological epoch.” Two years later, Crutzen restated the argument in an article in Nature titled “Geology of Mankind.”

The Anthropocene, Crutzen wrote, “could be said to have started in the latter part of the eighteenth century, when analyses of air trapped in polar ice showed the beginning of growing global concentrations of carbon dioxide and methane.”

Soon, the term began popping up in other scientific publications. “Riverine quality of the Anthropocene” was the title of a 2002 paper in the journal Aquatic Sciences.

“Soils and sediments in the anthropocene,” read the title of a 2004 editorial in the Journal of Soils and Sediments.

Jan Zalasiewicz, a geologist at the Britain’s University of Leicester, found the spread of the concept intriguing. “I noticed that Paul Crutzen’s term was

One argument against the idea is that humans have been changing the planet for a long time.

appearing in the serious literature, in papers in Science and such like, without inverted commas and without a sense of irony,” he recalled in a recent interview. At the time, Zalasiewicz was the head of the stratigraphic commission of the Geological Society of London. At a luncheon meeting of the commission, he asked his fellow stratigraphers what they thought of the idea.

“We simply discussed it,” he said. “And to my surprise, because these are technical geologists, a majority of us thought that there was something to this term.”

In 2008, Zalasiewicz and 20 other British geologists published an article in GSA Today, the magazine of the Geological Society of America, that asked: “Are we now living in the Anthropocene?” The answer, the group concluded, was probably yes: “Sufficient evidence has emerged of stratigraphically significant change (both elapsed and imminent) for recognition of the Anthropocene... as a new geological epoch to be considered for formalization.” (An epoch, in geological terms, is a relatively short span of time; a period, like the Cretaceous, can last for tens of millions of years, and an era, like the Mesozoic, for hundreds of millions.) The group pointed to changes in sedimentation rates, in ocean chemistry, in the climate, and in the global distribution of plants and animals as phenomena that would all leave lasting traces. Increasing carbon dioxide levels in the atmosphere, the group wrote, are predicted to lead to “global temperatures not encountered since the Tertiary,” the period that ended 2.6 million years ago.

Zalasiewicz now heads of the Anthropocene Working Group of the International Commission on Stratigraphy, which is looking into whether a new epoch should be officially designated, and if so, how. Traditionally, the boundaries between geological time periods have been established on the basis of changes in the fossil record — by, for example, the appearance of

“What’s going to happen in the 21st century could be even more significant,” a geologist says.

one type of commonly preserved organism or the disappearance of another. The process of naming the various periods and their various subsets is often quite contentious; for years, geologists have debated whether the Quaternary — the geological period that includes both the Holocene and its predecessor, the Pleistocene — ought to exist, or if the term ought to be abolished, in which case the Holocene and Pleistocene would become epochs of the Neogene, which began some 23 million years ago. (Just last year, the International Commission on Stratigraphy decided to keep the Quaternary, but to push back its boundary by almost a million years.)

In recent decades, the ICS has been trying to standardize the geological time scale by choosing a rock sequence in a particular place to serve as a marker. Thus, for example, the marker for the Calabrian stage of the Pleistocene can be found at 39.0385°N 17.1348°E, which is in the toe of the boot of Italy.

Since there is no rock record yet of the Anthropocene, its boundary would obviously have to be marked in a different way. The epoch could be said simply to have begun at a certain date, say 1800. Or its onset could be correlated to the first atomic tests, in the 1940s, which left behind a permanent record in the form of radioactive isotopes.

One argument against the idea that a new human-dominated epoch has recently begun is that humans have been changing the planet for a long time already, indeed practically since the start of the Holocene. People have been farming for 8,000 or 9,000 years, and some scientists — most notably William Ruddiman, of the University of Virginia — have proposed that this development already represents an impact on a geological scale. Alternatively, it could be argued that the Anthropocene has not yet arrived because human impacts on the planet are destined to be even greater 50 or a hundred years from now.

As the international community focuses on climate change as the great challenge of our era, it is ignoring another looming problem — the global crisis in land use. With agricultural practices causing massive ecological impact, writes Jonathan Foley, the world must find new ways to feed its burgeoning population and launch a “Greener” Revolution.READ MORE

“We’re still now debating whether we’ve actually got to the event horizon, because potentially what’s going to happen in the 21st century could be even more significant,” observed Mark Williams, a member of the Anthropocene Working Group who is also a geologist at the University of Leicester.

In general, Williams said, the reaction that the working group had received to its efforts so far has been positive. “Most of the geologists and stratigraphers that we’ve spoken with think it’s a very good idea in that they agree that the degree of change is very significant.”

Zalasiewicz said that even if new epoch is not formally designated, the exercise of considering it was still useful. “Really it’s a piece of science,” he said. “We’re trying to get some handle on the scale of contemporary change in its very largest context.”

COMMENTS

It's refreshing to read of scientists discussing man's impact on the environment in a context where the merits of one or the other hypothesis is not yet highly politicized. I'm glad that these geologists can discuss these physical changes on earth without the intervention of proto science and anti-science campaigners.

The thought occurs to me: Because these stratigraphers are generally discussing objects in a solid state rather than fluids like air and water, that non-scientists and non-specialist scientists will feel as though there is less to dispute. Climate scientists, however have to deal with more complex systems with their "fluid dynamics", which of necessity involve more statistical uncertainties. These uncertainties invite more "kibitzing" from outside. Therefore the whole issue of AGW denial, etc. Only time will tell, whether the concept of the Anthropocene will become a new common sense.

Posted by
Michael Hoexter
on 17 May 2010

We should give the planet another ice age cycle to cull the human species before we start naming things for ourselves.

110,000 years ago there was probably a fairly heavy human infestation with civilizational characteristics similar to our own, yet nothing (if you know of something, name it) survived their existence except us...wheel, lever/screw, music, sciences, etc.

While we still can, we should send to the moon a time capsule, made visible by an automatic, technology-free reflecting device, full of our ideas about an "anthropocene".

If the next, post-iceage human bloom can get there to read it, let them decide.

Posted by
Jeff L. Snyder
on 17 May 2010

Presumably if the Anthropocene is officially recognised, the Holocene will have to be renamed, since it won't be "wholly recent" anymore.

Posted by
Rob Clack
on 18 May 2010

A silly idea without any real scientific merit. However, since we can name and divide geological epochs in any manner we choose, why not make one "anthropocene." It certainly allows supposedly learned persons of supposed great intellect to spend time on this rather than having to dirty their hands with real research.

Posted by
Bob Greene
on 18 May 2010

If they are looking for a convenient starting point for this new epoch, perhaps they might consider the Columbian exchange? It signifies what might be the first instance of a truly hemispherical environmental human impact. The bi-directional flow between the Eastern and Western hemispheres permanently altered subsistence strategies, land use patterns, agricultural crops, trade networks, diet, health, and so on. And while it exerted its influence on a genuinely global scale, in many instances its effects had been wrought with relatively little objective recognition.

Posted by
Frank Spaulding
on 18 May 2010

Is a "spiral of silence" effectively vanquishing open discussion regarding scientific evidence of human population dynamics? Perhaps the last of the last taboos is human population dynamics.

Posted by
Steven Earl Salmony
on 19 May 2010

Several worldwide stratagraphic markers can be clearly discerned in the most recent geological record; airborne PB from the gasoline additives of the 1920's - 1960's and radionucleotides from the atmospheric atomic testing of the 1950's are two such markers that are, without doubt, anthropic in origin; many others including important extinctions will be discernable in the fossil record by our descendents; any geoscientist reading this can probably list many more; I think the case for the Anthropocene is both useful and compelling.

Posted by
William Nieter
on 20 May 2010

I second William Nieter's comment above. I, too, believe the "Anthorpocene" designation true an useful, and agree it should start withe the industrial revolution (the beginning of mass carbon extraction and release into the atmosphere) beginning at the end of the 18th century.

Posted by
racetoinfinity
on 05 Jul 2010

"It's refreshing to read of scientists discussing man's impact on the environment in a context where the merits of one or the other hypothesis is not yet highly politicized. I'm glad that these geologists can discuss these physical changes on earth without the intervention of proto science and anti-science campaigners. "

I so totally agree with this statement, Michael (Hoexter, 5/17/2010). Thanks....

Posted by
Gary D. Grammon
on 23 Feb 2011

Placing the boundary of the Anthropocene unambiguously at the middle of the 20th Century -1950 CE for sake of simplicity - makes sense. In the grand scheme of things, aren't the years between accumulation of gasoline lead in the atmosphere, the sudden bloom of atomic isotopes from bomb testing, and the spiking of atmospheric carbon dioxide as geologically simultaneous as the Chicxulub bollide impact and the demise of the great lizards?

Posted by
Paul M. Suckow
on 17 Jun 2011

Comments have been closed on this feature.

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